Vortex laser is a spiral phase beam, also known as a vortex beam. The vortex laser shows a spiral wavefront that changes in a spiral-like manner along the beam propagation direction and has a Poynting vector following a spiral trajectory around a beam axis.
It refers to the vortex beam having an arbitrary polarization and a spiral phase structure in a cross section. Compared with other beams, the vortex beam has special properties that can be used in many fields, such as high resolution imaging, laser precision machining, particle manipulation, data storage, and remote sensing.
There are many methods for generating vortex beams, such as static spiral phase plate (SPP), computer-generated holography, and mode conversion. Since conventional laser cavity can hardly generate a vortex beam directly, it must be modulated by a vortex element placed outside the laser cavity. The vortex beam generated by the mode conversion needs to be incident by the laser beam after shaping, such as Hermite-Gaussian beams, causing the system complex. The conversion efficiency of the static spiral phase plate is limited and the quality of the vortex beam is poor. In addition, holography is widely used, however, its diffraction efficiency is low, and the light path of the diffractive element is complicated so that the quality of the vortex beam is poor.
As a result, it is necessary to provide a vortex laser generation device in a degenerate cavity with a spiral phase element and a vortex laser generation method to solve the problems existing in the conventional technologies, as described above.